Power hand tool

ABSTRACT

A power hand tool includes a housing containing a motor, a speed changing gear set coupled to the power output end of the motor, a transmission mechanism coupled to the speed changing gear set and partially extending out of the housing for operation by the user to selectively shift the speed changing gear set to one of a series of gearshift positions thereof, a set of index signs marked on the transmission mechanism corresponding to the series of gearshift positions and alternatively moved to a sighthole in the housing subject to the gearshift position of the speed changing gear set, and a light emitting device mounted in the housing adjacent to the sighthole for illuminating one index sign of the transmission mechanism that is in alignment with the sighthole.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a hand tool and more particularly, to apower hand tool having a transmission position indicator (gearshiftposition indicator) that can be recognized clearly.

2. Description of the Related Art

Regular power hand tools are commonly provided with a multi-step speedchanger (transmission) that is controllable to change the revolvingspeed of the output shaft subject to different working requirements.

The multi-step speed changer of a conventional power hand tool has anoperating knob disposed at one side for operation by the user to changethe gearshift position. The operating knob has marked thereon indexsigns, for example, H for high speed, M for standard speed and L for lowspeed, or a series of numerical signs such as 1, 2, 3, etc. forindicating the current gearshift position. However, one may work with apower hand tool in the night or under a dark environment. When workingin the night or under a dark environment, the user may be unable to seethe indication of the respective index sign well. If the user directlyuses the power hand tool that is shifted to a wrong gearshift position(wrong revolving speed), a working mistake or accidental injury mayoccur.

SUMMARY OF THE INVENTION

The present invention has been accomplished under the circumstances inview. It is therefore an object of the present invention to provide apower hand tool, which enables the user to see the adjusted gearshiftposition clearly when in the dark.

To achieve this object of the present invention, the power hand toolcomprises a housing having a through hole and a sighthole, a motorfixedly mounted inside the housing and having a power output end, amulti-step speed changer, and an indicator. The multi-step speed changerhas a speed changing gear set coupled to the power output end of themotor, and a transmission mechanism coupled to the speed changing gearset and partially extending out of the through hole of the housing foroperation by the user to selectively shift the speed changing gear setto one of a series of gearshift positions thereof. The transmissionmechanism has a series of index signs corresponding to the gearshiftpositions, and the index signs are alternatively moved to the sightholesubject to the gearshift positions of the speed changing gear set. Theindicator has a light emitting device mounted in the housing adjacent tothe sighthole for illuminating one of the index signs of thetransmission mechanism that is moved to the sighthole.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a power hand tool according to apreferred embodiment of the present invention, wherein a part of thehousing is removed for illustration purpose.

FIG. 2 is a side view of FIG. 1.

FIG. 3 is top view of the power hand tool according to the preferredembodiment of the present invention.

FIG. 4 is similar to FIG. 3 but showing the gearshift position changed.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1-4, a power hand tool in accordance with a preferredembodiment of the present invention is shown comprising a housing 10, amotor 20, a multi-step speed changer 30, an indicator 40, and a batterypack 50.

The housing 10 has a through hole 11 and a sighthole 12 at one side, forexample, the top side. Further, the housing 10 defines therein aplurality of receiving chambers.

The motor 20 is fixedly mounted inside the housing 10, having a poweroutput end for output of a rotary driving force to the outside.

The multi-step speed changer 30 comprises a speed changing gear set 31and a transmission mechanism 32. The speed changing gear set 31 ismounted inside the housing 10 and coupled to the power output end of themotor 20 for selectively changing the rotary driving force (constantrevolving speed) to different revolving speeds (because this speedchanging gear set is of the known art, no further detailed descriptionin this regards is necessary). The transmission mechanism 32 comprises agearshift control bar 321 and a transmission shaft 322. The gearshiftcontrol bar 321 is axially slidably mounted inside the housing 10,having an operating knob 323 disposed at one side thereof and extendingthrough the through hole 11 to the outside of the housing 10 foroperation by an external force (the user) to move the gearshift controlbar 321 axially forwards or backwards. The gearshift control bar 321 hasmarked thereon index signs 324 (for example, H/M/L, or a series ofnumerical signs such as 1, 2, 3, etc.) corresponding to the gearshiftpositions provided by the speed changing gear set 31. Through thesighthole 12, one of the index signs 324 can be seen. The transmissionshaft 322 has the two distal ends thereof respectively coupled to thespeed changing gear set 31 and the gearshift control bar 321. Whenoperating the operating knob 323 to move the gearshift control bar 321,the transmission shaft 322 is moved to change the gearshift position andat the same time the corresponding index sign 324 is moved intoalignment with the sighthole 12. Therefore, when operating the operatingknob 323 to change the gearshift position (revolving speed), the usercan see the corresponding index sign 324 through the sighthole 12.

The indicator 40 comprises a light emitting device 41 and alight-transmissible covering 42. The light emitting device 41 accordingto this embodiment is an LED (light emitting diode) mounted in thehousing 10 near the sighthole 12. The light-transmissible covering 42according to this embodiment is a convex lens mounted in the sighthole12 and adapted to magnify the image of the index sign 324 that isvisible through the sighthole 12.

The battery pack 50 is mounted inside the housing 10 and electricallycoupled to the motor 20 and the light emitting device 41 of theindicator 40 to provide the motor 20 and the light emitting device 41with the necessary working voltage, enabling the motor 20 to provide arotary driving force and the light emitting device 41 to give off light.

The operation of the present invention is outlined hereinafter withreference to FIGS. 3 and 4 again. When operating the operating knob 323to shift the gearshift control bar 321 and to further drive thetransmission shaft 322 to change the gearshift position, thecorresponding index sign 324 is moved into alignment with the sighthole12, and at the same time the light emitted from the light emittingdevice 41 will stream on the index sign 324, and therefore the user cansee the corresponding index sign 324 through the light-transmissiblecovering 42. By means of the illumination of the light emitting device41 and the magnifying effect of the light-transmissible covering 42, theuser can see the corresponding index sign 324 clearly when working inthe dark.

1. A power hand tool comprising: a housing having a through hole and a sighthole; a motor fixedly mounted inside said housing, said motor having a power output end for outputting a rotary driving force at a predetermined revolving speed; a multi-step speed changer having a speed changing gear set coupled to the power output end of said motor, and a transmission mechanism coupled to said speed changing gear set and partially extending out of said through hole of said housing for operation by the user to selectively shift said speed changing gear set to one of a series of gearshift positions thereof, said transmission mechanism having a series of index signs corresponding to said gearshift positions, said index signs being alternatively moved to said sighthole subject to the gearshift positions of said speed changing gear set; and an indicator having a light emitting device mounted in said housing adjacent to said sighthole for illuminating one of said index signs of said transmission mechanism that is moved to said sighthole.
 2. The power hand tool as claimed in claim 1, further comprising a battery pack mounted inside said housing and electrically coupled to said motor and said light emitting device to provide the necessary working electricity to said motor and said light emitting device.
 3. The power hand tool as claimed in claim 1, wherein said indicator further comprises a light-transmissible covering mounted in said sighthole for magnifying the image of the index sign of said transmission mechanism that is moved to said sighthole.
 4. The power hand tool as claimed in claim 3, wherein said light-transmissible covering is a convex lens.
 5. The power hand tool as claimed in claim 1, wherein said transmission mechanism comprises a gearshift control bar axially slidably mounted inside said housing, said gearshift control bar having an operating knob disposed at one side thereof and extending out of said housing through said through hole for operation by the user to move said gearshift control bar axially forwards or backwards, and a transmission shaft coupled between said speed changing gear set and said gearshift control bar and movable by said gearshift control bar to change the gearshift position of said speed changing gear set; wherein said index signs are marked on said gearshift control bar and alternatively shifted with said gearshift control bar to said sighthole.
 6. The power hand tool as claimed in claim 1, wherein said light emitting device is a light emitting diode. 